The present invention relates generally to electronic ice bank controls and to voltage sensing controls.
Ice banks that are formed on evaporators for providing a cooling reserve, as used in the beverage dispensing industry, are well known. The size of an ice bank is typically regulated by one or more sensors placed at critical positions around an outer perimeter thereof. Conductivity sensors are known and are used in this regard to determine the presence of ice or water by virtue of the conductivity between a pair of probes. Thus, if ice forms between the probes the sensed conductivity will be relatively low, and if water is present there between, the sensed conductivity will be much greater. Therefore, if ice is sensed, the ice bank is presumed to be of adequate size and the refrigeration compressor, that is used to cool the evaporator and form ice thereon, can be shut off. Conversely, if water is sensed, the compressor is turned on to build ice until ice is again sensed. Naturally, such controls have delay times programmed therein to prevent destructive short cycling of the compressor.
It is also well understood that it can be harmful to a compressor if it is made to run at a voltage that is outside, above or below, the voltage range for which it is designed. This situation is common for beverage dispensing equipment used in remote areas where line voltage can fluctuate dramatically. Buck/Boost systems, that attempt to lower or raise the voltage, respectively, have been attempted, but without great success do to the complexity and cost thereof. Adding a voltage sensing system that can turn the compressor off if its voltage design limits are exceeded, is also a possibility. However, the cost of an additional electronic control can be unacceptable. Especially where such an additional control would need to become a standard part of all such dispensers, many of which will experience no need therefor. It is also generally too expensive to provide such voltage sensing as a custom feature. Accordingly, it would be desirable to have a cost effective control for an ice bank that both regulates the size thereof, that protects the compressor against short cycling and from operating at voltages outside its design specification.
The present invention is an apparatus and method that regulates the size of an ice bank and that prevents short cycling of the compressor and operation thereof at undesired voltages. A microprocessor based control circuit includes a circuit for sensing line voltage combined with an ice bank sensing circuit. The ice bank sensing circuit is of the conductivity sensing type wherein the electrical conductivity between two probes is sensed. Thus, the microprocessor continually monitors the probes to determine if refrigeration is needed or not, and continually senses the line voltage to determine if the voltage is within the design limits of the refrigeration compressor. The voltage sensing circuit can also sense if power has been interrupted where the voltage drops to zero.
In operation, the present invention will turn on the compressor if the ice bank sensor indicates water is present between the probes, the voltage is within operating limits and if a predetermined time delay has elapsed since the last compressor shut down. The compressor is turned off if, during operation thereof, the ice bank is of sufficient size, the voltage goes outside of design limits or there is a power failure. It can be appreciated that the voltage sensing circuit can be comprised essentially of a relatively inexpensive voltage divider circuit of a dedicated transformer. Therefore, the present invention utilizes the inexpensive combination of such a voltage sensing circuitry with a conductivity/ice sensing circuit to provide for an ice bank control that is more protective of the compressor with respect to both short cycling and operating at voltages outside the manufacturer""s recommended specifications, than is found in prior art ice bank sensing controls. Since the improved control of the present invention is relatively inexpensive, it can be used as a standard item rather than as a more costly custom or add on feature.